Geometry Nodes and Exporting (Creating a mesh) in Blender 2.92
Ok, after filing a bug report with Blender, I got a partial answer from HQ.

To get the instance geometry from the modifier, use the &quot;Make Instances Real&quot; operator. Applying modifiers on point clouds isn't supported yet.  For the other parts, we have this task: T85281.

This doesn't seem to directly address the export issue, but it's a start. For more info, head over to Task T85281 : Support piping legacy modifiers with the geometry nodes modifiers.